1. Field of the Invention
The present invention generally relates to a chemical mechanical polishing (CMP) system and, more particularly, to a chemical supply apparatus and method in the CMP system.
2. Background of the Invention
In the manufacturing of high-density integrated circuits, effective device isolation typically requires a global planarization process step in order to implement multilevel interconnections. A chemical mechanical polishing (CMP) technique is an effective way to achieve such planarization. Such polishing methods are well known to those skilled in the art and include the steps of closely attaching one side of a wafer to a carrier or a flat surface of a chuck and pressurizing the other side of the wafer toward a flat polishing surface.
During CMP processes, however, micro-scratches are created on a semiconductor wafer surface. These micro-scratches may cause degradation of product quality and yield. The major causes of the micro-scratches are the intrinsic characteristics of a slurry supply apparatus and a characteristic change in a slurry resulting from shear stresses generated in the CMP system.
A slurry supply apparatus in a conventional CMP system uses peristaltic pumps in order to feed polishing chemicals onto a semiconductor wafer.
FIG. 1 illustrates a cross-sectional view of a peristaltic pump 400 used in a slurry supply apparatus in a conventional CMP system. Slurry is supplied through a flexible tube 410. The slurry stays in the flexible tube 410 and makes no contact with any part of the peristaltic pump 400. One end of the flexible tube 410 is connected to an input part of the peristaltic pump 400, and the other end is connected to an output part of the peripheral pump 400. Because the flexible tube 410 is abraded by repeated shrinkage and extension, the peristaltic pump 400 suffers from a danger of slurry leakage due to degradations, such as cracking or breakage, in the flexible tube 410 inside the peristaltic pump 400. In order to reduce this danger, the flexible tube 410 is frequently exchanged with a new flexible tube.
Another drawback with conventional CMP systems is that pressures generated while driving the peristaltic pump 400 cakes particles in the slurry to clog a pipe or the flexible tube 410. Moreover, grains produced by contaminants or slurry caked by tube abrasion may be supplied onto a wafer to cause process defects.
As described above, in a slurry supply apparatus using the peristaltic pump 400, a flexible tube is abraded to cause tube failure, and frequent tube exchange lowers a system""s operating rate and increases the cost of operation. Moreover, an accuracy of the CMP process is lowered due to the use of the peristaltic pump 410.
Therefore, a current CMP process trend is to use chemical additives to form mixed slurries (e.g., ceria slurry, alumina slurry, etc.). Unfortunately, the chemical additive mixed slurry or slurry using a chemical element without a polishing element results in a settling phenomenon or a particle coagulation phenomenon that becomes more severe with the lapse of time than in the case with silica slurry. Since most current slurry supply apparatuses have a supply-following-mixture structure, they are not suitable for supplying the chemical additive mixed slurry.
A feature of an embodiment of the present invention is to provide a chemical supply apparatus and method in a semiconductor manufacturing process, using a self-supply pressure generated during chemical supply without a pump for forcibly supplying a chemical.
Another feature of an embodiment of the present invention is to provide a chemical supply apparatus and method in a semiconductor manufacturing process, that enables a chemical additive mixed slurry to suppress a settling phenomenon or a coagulation phenomenon that occurs with the lapse of time.
According to an aspect of the present invention, a chemical supply apparatus supplies a constant amount of chemical to a chemical injection part using a pressure of a pump-less chemical supply source. Means for measuring and controlling is mounted in a feed line to measure and control a flow rate of the supplied chemical in a proportional integral derivative (PID) automatic control manner.
In a preferred embodiment, the feed line further comprises a recycle line for preventing coagulation of the chemical and a branch line connected to the recycle line. The recycle line is preferably connected to the chemical supply source, and the branch line is connected to the chemical injection part via a measuring/controlling means. The measuring/controlling means comprises a flow rate control valve, a detector for detecting the flow rate of a chemical solution and generating flow rate data signals, and a controller for receiving the flow rate data signals and comparing the flow rate data signals with a reference flow rate data signal in order to output a control signal for controlling a degree of opening the flow rate control valve. The detector is mounted in or upon the feed line of the flow rate control valve
According to a second embodiment of the present invention, an apparatus for supplying chemicals to a chemical injection part in a semiconductor manufacturing process comprises a plurality of chemical supply sources, each chemical supply source containing a different chemical solution, and a plurality of associated feed lines. The chemical solutions are preferably injected from the chemical supply sources to the chemical injection part using a pressure at the chemical supply sources. Flow is controlled using a means for measuring/controlling flow rates of the chemical solutions supplied to the chemical injection part. The measuring/controlling means may be mounted in or upon each of the feed lines.
In the second embodiment, each of the chemical solution feed lines comprises a recycle line for preventing coagulation of the chemical solution and a branch line branching from the recycle line. The recycle line is connected to the chemical supply source, and the branch line is connected to the chemical injection part.
A chemical supply method using the chemical supply apparatus according to the second embodiment of the present invention comprises the steps of providing a pressure to a plurality of chemical supply sources, respectively carrying chemical solutions from the chemical supply sources to a plurality of feed lines using the pressure, respectively measuring/controlling flow rates of the chemical solutions carried through the feed lines, and mixing the measured/controlled chemical solutions just before being supplied to the chemical injection part.
In the embodiments, the step of measuring/controlling the flow rates comprises the steps of detecting a flow rate of a chemical solution flowing into the feed line, receiving a data signal corresponding to the detected flow rate and comparing the data signal with a reference flow rate data signal in order to output a control signal for controlling a degree of opening a flow rate control valve in order to control the flow rate of the chemical solution.
These and other features of the present invention will be readily apparent to those of ordinary skill in the art upon review of the detailed description that follows.